American Welding Society Forum
I'm constantly confronted by people that confuse the tensile strength numbers for the electrode identification system with hardness. Can anyone direct me to a chart, graph or information comparing the weld metal hardness, or the Rockwell numbers, for electrodes such as 7018, 8018, and 9018?
For carbon and low alloy steels there is a direct relation between hardness and tensile strength. I can't remember the number but will revise this post when I find them.
It sounds like you are asking for a chart that tells you, what is the weld metal hardness for a given electrode (i.e. 7018, 8018). If I am assuming correctly, the answer is there isn't one (at least that I am aware of).
Weld metal hardness is dependent on more that just the welding rod used. The final weld hardness is more dependent on the type of base metal you are welding, how many passes you apply, (dilution) the heat input, preheat (if applied), PWHT of the weld, and so on.
There are however, Hardness-Tensile strength conversion charts available that will show you the correlation between hardness and tensile strength. These are not for any specific welding rod however. They are just general hardness numbers. For example A Vickers hardness of 190 = a Brinell hardness of 181 which = a Tensile strength of 88 ksi.
Just type the key word "Hardness Conversions" into any search engine and you should be able to find such a table. I have one from www.radiatronics.com.
M-Squared, That's exactly what I'm looking for. Thanks.
Have e-mailed you a scanned copy of an old conversion chart that I have lying around here at home. I have a newer version, but it is at the office. If you would prefer that one, I can try to get it to you as well.
As M Squared correctly points out, there are quite a few "Hardness vs. Tensile Strength" conversion tables for general use (i.e., not developed especially for welds), and I can send you one, if you wish.
However, you must bear in mind that those tables ARE ONLY APPROXIMATE, i.e. they can be used for making rough estimates or to have an idea of the figures, BUT NEVER for design or calculation purposes. ASTM standards which rule hardness measurements are very clear on that subject.
Giovanni S. Crisi
Sao Paulo - Brazil
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